1. Field of the Invention
The present invention relates to display devices, and more particularly, relates to a display device including a substrate provided with light-emitting devices and a sealing substrate which is adhered to the substrate and to a method for manufacturing the display device.
2. Description of the Related Art
As a next-generation display device, a display device using organic electroluminescent devices has drawn attention. This display device has the following various features: the viewing angle is wide since self-luminous organic electroluminescent devices are used, energy saving may be obtained since a backlight is not necessary, the responsibility is high, the thickness of the device itself may be decreased, and the like. In addition, when this display device uses a plastic substrate as a substrate on which organic electroluminescent devices are provided, a flexible display device can be realized using inherent flexible properties of an organic material forming light-emitting devices.
Since having very inferior moisture resistance, the organic electroluminescent device of the display device described above is liable to be degraded by moisture present in the air, and as a result, problems may arise in that areas (dark spots) are generated which do not emit light, the brightness is decreased, and the like. Hence, a sealing technique has been necessary in most cases in order to prevent the entry of moisture into a display region in which the organic electroluminescent devices are provided.
Accordingly, for example, a complete solid sealing structure in which organic electroluminescent devices are sealed in a resin material has been proposed, the structure being formed by the steps of applying the resin material used as an adhesive onto a base substrate so as to cover the organic electroluminescent devices provided thereon, and then adhering a sealing substrate to the base substrate with the above resin material provide therebetween. In the structure described above, no spaces that may allow the entry of moisture are present between the above two substrates that enclose the organic electroluminescent devices, and as a result, the problems described above can be effectively prevented.
In addition, as a method for manufacturing a display device having the complete solid sealing structure described above, a method has been proposed which has the steps of applying an adhesive for display devices, which is formed using a photocurable composition, on one major surface of a sealing substrate, irradiating light to this adhesive for activation, and then adhering a base substrate to the sealing substrate with the adhesive provided therebetween while the light is being blocked. According to this method, while organic electroluminescent devices formed at the base substrate side are prevented from degradation which is caused by exposure to the light, the organic electroluminescent devices can be sealed in the adhesive (see Japanese Unexamined Patent Application Publication No. 2004-231957).
In manufacturing a display device having the complete solid sealing structure as described above, when an adhesive resin before curing flows and adheres onto terminals (terminal electrodes) for external connection extending from the organic electroluminescent devices, the connection between the display device and an external device with the terminal electrodes provided therebetween becomes unstable. Hence, in the manufacturing process described above, while the terminal electrodes are covered with a masking tape, the sequential steps described above have been carried out. As a result, the adhesion of the adhesive resin onto the terminal electrodes is prevented.